缺词填空 先通读下列短文，掌握其大意，然后根据短文内容和所给首字母，在空格内填入一个适当的词，使短文意思完整。所填单词在题后横线上必须完整写出（本大题共6分，每格0.5分）
Suppose you are reading a book. Suppose you suddenly close your eyes, can you still see the book? "Of course not." you will say. But can you tell why? You would p__小题1: say, "When I close my eyes, my e__小题2:___ cannot get out of my eyes to get to the book." Many others might give an explanation(解释) very much like the above . But this explanation is w__小题3:___.
You cannot see any object if light from that object doesn’t get into your eyes. Some of the things you see give off light of their own.
The sun, the star, a lighted lamp are examples that can be seen by their own light. 
S__小题4:__ things are luminous(发光的). Most of the things you see are not giving off light of their own. They are simply reflecting(反射) light that falls on them from the sun or some other luminous bodies. The moon, for example, doesn't give off any light of i__小题5:_ own. It's non-luminous. You see it because sunlight falls on it and some of it reflects in your d__小题6:__. So moonlight is only second-hand sunlight.
When you look at a book, it sends to your eyes some of the light which falls on it, and you see the book. If light could be kept out from w__小题7:__ you are, so that there would be no light for the book to reflect, then you could not see the book e__小题8:__ with your eyes wide open.
Light travels so fast that the time it t___小题9:__ from the book to your eyes is so s___小题10:_ as if there was none at all. Light r___小题11:__ us from the moon, which is about 380,000 kilometers away, in only a little more than a s__小题12:__.
